Decorative metal plating



Feb. 5, 1957 s s, FREY 2,780,591

DECORATIVE METAL PLATING Filed Nov. 6, 1955 killin... wal

INVENTOR `@Ww/5L 5. F/asy,

United States Patent O DECDRATIVE METAL PLATIN G Samuel S.` Frey, Elizabeth, N. J., assigner to Oakite Products Incorporated, New York, N. Y.

Application November 6, 1953, Serial No. 390,630

8 Claims. (Cl. 204-23) The present invention relates to a novel metal plating process for producing a decorative electroplated metal finish on metal objects and more particularly to a process wherein a polished and cleaned metal surface is first conditioned anodically to produce an invisible film thereon and then plated in a bright nickel bath whereby a patterned semi-bright nickel plating is produced.

It is an object `of the invention to provide a process for the production of a novel decorative finish for metallic electro deposits.

It is a further object of the invention to provide a process whereby the surface of common plated metals is given a pleasing matte-like finish.

It is `a further object of the invention to provide a process whereby letters, numbers or other configurations can be easily reproduced on electroplated surfaces.

In accordance with the invention it has unexpectedly been discovered that electroplated decorative nishes can be produced on metal objects, such as, for example, brass, copper and steel, from normal bright nickel plating baths if the articles are preconditioned by an anodic treatment in an alkaline silicaceous bath to produce an invisible film thereon before they `are electroplated in the bright nickel bath.

The invisible film produced by the anodic preconditioning treatment is one that is invisible to the naked eye and somewhat ditiicult to detect with the ordinary microscope. However, when nickel is electroplated thereover, patterns of various sized grain structure and different degrees of uniformity are produced in the nickel plate. The intensity of the pattern developed in the nickel coating depends upon the concentration and composition of the nickel plating baths and upon the thickness of the anodic film produced by the preconditioning treatment. The thickness of the anodic film can be controlled by the teniperature, time, current density and composition of the conditioning bath.

In carrying out the process according to the invention, the metal object to be given the decorative plating is first given a smooth clean finish, for example, by polishing and cleaning in the ordinary manner to provide a round metallic surface free of grease, dirt and oxide. The cleaning, for example, can be carried out with the usual inhibited alkaline cleaners by soaking therein followed by a cathodic treatment therein or with vapor degreasers such as trichloroethylene. It is also possible to carry out the cleaning of the metal in the same bath as is employed for the anodic preconditioning treatment according to the invention by giving it a cathodic treatment therein before it is made the' anode for the anodic treatment. This cleaning method, however, is less preferred than using a separate alkaline cleaning bath, as the dirt removed during the cleaning cycle accumulates in the conditioning bath and shortens its life.

After the metal object has been cleaned, it is then introduced into an alkaline silicaceous bath wherein it is made the anode until an anodic film is formed sulirice cient to provide a patterned eiect when such precondi* tioned object is nickel plated. As the resulting anodic film is invisible, the only way to be certain that the de= sired lilm is formed is by routine testing of the preconditioned object by applying a nickel plate thereover. Anodic preconditioning treatments carried out under predetermined conditions, i. e. time, temperature, cum-ent density, composition or' bath, will give uniform results in the subsequent nickel plating under predetermined conditions.

The essential feature of the preconditioning bath is that it contain a soluble silicaceous material such as silicates, metasilicates, colloidal silica gel or hydrated silica and the like and that the pH of such bath is adjusted to a value between 10.25 and 12.2 (electronically).

The quantity of silicaceous material employed can be varied considerably, but generally quantities sufficient to provide between about 2 g. and 20 g. of SiOz per liter of bath have been found desirable. Generally, the greater the concentration of the silicaceous material, the denser will be the pattern produced in the subsequent nickel plate.

In order to provide the proper conductivity and pH of between 10.25 and 12.2, preferably between 10.75 and 12.0, salts, hydroxides or acids can be added. Some salts, however, are less preferred as additions to the condi tioning baths as they may tend to have a corrosive action on the metal surface treated and affect the uniformity of the anodic lm. For example, sulfates, chlorides, citrates and acetates may give adverse results.

The current densities employed for the anodic preconditioning treatment can, for example, vary between 0.1 ampere per square foot to over 18 amperes per square foot. The best pattern etects were obtained upon subsequent nickel plating when the anodic preconditioning treatment was carried out in the lower range of current densities. Operating voltages of l to 3 Volts have, for example, been found suitable.

The time of anodic treatment has an effect upon the character of the pattern produced in the subsequent nickel plating. In general the time should be the shorter, the higher the current density employed. Anodic treatments varying from -two to sixty seconds have been found suitable for the process according to the invention. Anodic preconditioning treatments at too high a current density and too long a period can result that the subsequent nickel plate is dull and without pattern effects.

The temperatures employed for the' anodic preconditioning treatment can vary between room temperature and the boiling point of the preconditioning bath; the best effects, however, have been obtained with a bath operating at a temperature between about to 180 F.

Various silicaceous materials have been found suitable for the preparation of the anodic preconditioning baths, such as, for example, sodium orpotassium silicateswith NazO or KzO/SiOz ratios ranging from 2:1 to 1:5 as well as colloidal silica gel or hydrated silica, such as, for example, is sold under the tradename Ludox which com tains approximately 30% SiOa.

Sodium and potassium phosphates, carbonates, borates,

hydroxides and phosphoric acid have, for example, been found suitable for adjusting the pH and conductivity of the silicaceous preconditioning baths.

After the metal objects have been preconditioned by the ano-dic treatment in the silicaceous bath they should be immediately rinsed with water While still Wet and given the usual acid dip and rinse before being introduced into the nickel plating bath. Drying of the preconditioning bath solution upon the preconditioned articles can tend to leave a deleterious dry Adown pattern which is dicult to risen off either with water or the usual mineral acids.

The nickel plating of the preconditioned metal objects canV be carried out in any of the usual bright nickel plating baths under usual conditions. The decorative pattern will appear in the nickel plate after a few hundredths of a mil have been-plated and becomes pronounced aty a thickness between 0.1 and 0.25 mil. With plating thickness over 0.25 mil the pattern tends to become less pronounced.

While the patternedteffect according to the invention is only obtained upon the preconditioned metal objects upon subsequent electroplating with nickel, it is possible to produce similar pattern effects in other metallic platings by subjecting the patterned nickel plated object produced according to the invention to further electroplating to produce thin electroplates of other metals such as, for example, gold, copper, chromium and the like thereover from bright metal plating baths.

The patterned electroplatings obtained according to the invention are rmly adherentA to the metal base. 'f he patterning effect is not destroyed if a thin coating of clear lacquer is applied thereover should protection of the electroplated surface-be desired.

If itis desired to modify the pattern effects obtainable according to the invention, this may be simply done by pressing letters, numbers or words or other configurations into the wet anodic film produced by the preconditioning while the other areas not soon touched will appear with the pattern effect according to the invention. Of course, similar effects could also be obtained with the aid of the usual masking tapes or iiuids customarily used in the metal finishing arts.

The accompanying drawings show by way of example several of the pattern effects obtainable according to the invention.

In the drawings:

Fig. 1 shows a metal panel carrying a typical pattern effect obtainable according to the invention,

Fig. 2 shows a metal panel carrying another pattern effect obtainable according to the invention, and

Fig.l 3 shows a metal panel in which the patterned effect obtainable according to the invention is interrupted by bright plated areas obtained by pressing the wet anodic film with a rubber stamp prior to the nickel plating treatment. As will be seen from the drawings, the patterned eiect obtained according to the invention provided a crackle-like finish which in some respects resembles a y Example 1 A brass panel of zinc and 70% copper was buted to a high degree of luster and then soaked for several minutes in a customarily inhibited alkaline cleaner at 200 F. followed by a power rinse in Warm water, and cathodically cleaned in such alkaline cleaner at a current density of 60 amperes per square foot for about 30 sec onds at 180 F. The panel was then rinsed with cold water, dipped ten seconds in 10% hydrochloric acid and again rinsed with cold water. The cleaned panel was then transferred to an aqueous solution containing g./l. of a mixture containing 40% of sodium metasilicate (NaaSiOs-SHzO) and of borax (NaaBtOr-IOHZO), where it was given a twenty-five second treatment as the anode at an average current density of 0.6 ampere per square foot. Thereafter, the conditioned panel was rapidly transferred to a coldrunning water rinse and allowed to remain therefor 1 minute. Thisvwas followed by` a dip into 10% HClV and a cold running water rinse.

The panel was then immersed carefully into a nickel plating bath of the following composition.

NiSO4-7H2O 274.7 g./l. NiClzHzO 58.6 g./l. H3BO3 40.3 g./l. Duponal ME l 0.4 g./ 1. Sodium O-benzoic suliimide 1.0 g./l.

H2SO4 Sufficient to give a pH between 2.5 and 3.5.

l surface active agent mainly consisting oi' sodium lauryl :su ll ouate.

A nickel electrodeposit was formed in tenl minutes under a current densityy of 30 a. s. f. without agitation. After rinsing the nickel solution off, the panel was dipped in dilute hydrochloric acid solution, rinsed again and then immersed in a chromium plating bath (250 g./l. CrOs and 2.5 g./l. of S04) for 4 minutes to receive a bright thin chromium plate. A pleasing decorative pattern of decorative value of the type shown in Fig. 1 appeared through the plate.

Example 2 A buifed brass panel of 30% zinc and 70% copper Was cleaned as in Example 1 and then transferred to an aqueous anodizing bath containing 18 g./l. of NazSiO3-5H2O and 27 g./l. Na2B4O7-l0H2O- The panel was anodized therein for 15 seconds at a temperature of 180 F. at an average current density of 0.6 a. s. f. The resulting anodized panel was immediately given a cold running water rinse and then nickel plated in a bright nickel plating bath of the same composition as in Example 1 for ten minutes at 130 F. at an average current density of 30 a. s. f. to produce a nickel plate approximately 0.25 mil thick. The plated panel was rinsed and` dried and revealed a uniform decorative pattern.

Example 3 A butfed brass panel of 30% zinc and 70% copper was cleaned as in Example l and transferred to an aqueous anodizing bath containing g./l. of a mixture containing 20 hydrated sodium metasilicate and 80% anhydrous di-sodium hydrogen phosphate. The panel was anodized therein for 25 seconds at a temperature of 180 F. and a current density of 0.6 a. s. f. During the anodizing treatment the voltage varied from 1.1 to 1.8 voltsto maintain a constant current density. No agitation of the work or solution was employed.

The anodized panel was then immediately rinsed with running cold water for one minute, dipped in 10% HCl for 10 seconds and rinsed again with water.

The rinsedpanel was then plated in a nickel plating bath of the following composition.

G./l. NiSO4.7H2O 274.7 NiCl2.6H2O 58.6 HaBOg 40.3 Duponal ME 0.4 Sodium o-benzoic sultmide 2.0

This bath was operated at F. with a cathodic current density of 28-30 a. s. f. until a nickel plating about 0.00025 thick was produced. The thus nickel-plated panel after rinsing was then given a bright chromium plating. The resulting chrome plated iinish was rinsed and dried revealing a pattern in the final plate that was semi-lustrous and decorative.

Example 4 A buifed brass panel of 30% zinc and 70% copper was cleaned as in Example l and then transferred to an aqueous anodizing bath containing 45 g./l. of a mixture containing 40% of anhydrous sodium carbonate and 60% of Ludox. The panel was anodized therein for l5 seconds under a constant voltage of 1 volt. Thereafter the anodized panelwas immediately rinsed with cold water agement.

and dipped and rinsedagain and then given a nickel plate 0.00025" Vthickness in a nickel plating bath of the same composition as Example 3 at a current density of about 30 a. s. f. The thus nickel plated panel wasthen given a chromium ash plate of high luster over the nickel plate from a chromic acid sulfuric acid bath of normal concentrations. After rinsing and drying, the finished surface possessed a pleasing decorative pattern.

Example A huied brass panel of 30% zinc and 70% copper was cleaned as in Example 1, and then transferred to an aqueous anodizing bath of the same composition `as that of Example 4. The panel was anodized therein for 20 seconds at 180 F. at a constant current density of 0.6 a. s. f. Thereafter, the anodized panel was immediately rinsed, acid dipped and rinsed again and then given a nickel plate 0.25 mil thick in a nickel plating bath of the same composition as in Example 3. The nickel plated panel was then given a ch-romium plate as in Example 4. After rinsing and drying the panel has a pleasing decorative pattern similar to that of Example 4, but of slightly smaller grain size.

Example 6 A buffed brass panel of 30% zinc and 70% copper was cleaned as in. Example 1 and then transferred to an aqueous anodizing bath containing 45 g./1. of a mixture of 40% of hydrated trisodium phosphate and 60% of sodium silicate G (average composition NazO 19.4%, SiOz 62.5%, H2O 17.5%). The panel was anodized therein for 15 seconds at 180 F. and at a voltage of l volt. Thereafter the anodized panel was rinsed, acid dipped and rinsed again, and transferred to a nickel plating bath of the same composition as in Example 3 and allowed to remain therein for 1 minute before applying a current of 30 a. s. f. for 10 minutes. The resulting nickel plated panel was then rinsed, acid dipped and rinsed again and then placed in a chrome plating bath where it was plated for 4 minutes at 104 F. and 100 a. s. f. The pattern developed on the panel was of similar appearance to that of Examples 4 and 5, but had a still smaller grain size.

Example 7 A buifed brass panel of 30% zinc and 70% copper was cleaned as in Example 1 and then transferred to an anodizing bath containing 45 g./l. of a mixture of 20% anhydrous sodium carbonate and 80% Kasl No. 6 (a potassium silicate containing 26.80% Si02). The panel was anodized therein for 15 seconds at 1 volt employing a steel cathode. The current density varied between 0.12 and 0.6 a. s. f. decreasing as the time increased. The anodized panel was then immediately rinsed, acid dipped and rinsed again and introduced into a nickel plating bath of the same composition as in Example 1 and plated therein for minutes at 30 a. s. f. A chromium plate followed the nickel plate. The finished nickel and chromium' plated panels surface had a pleasing pattern in which the grains were somewhat elongated as shown in Fig. 2.

Example 8 A buled brass panel of 30% zinc and 70% copper was cleaned as in Example 1 and then transferred to an anodizing bath containing 9 g. of Kasil No. 6 and 36 g. of anhydrous sodium carbonate per liter. The panel was anodized therein at 180 F. for 15 seconds under a constant voltage of 1 volt. rl`he anodized panel was immediately rinsed and dipped, and rinsed again and given a nickel plate 0.2 mil thick from a nickel plating bath of the same composition as in Example l. The nickel plated panel was then copper plated in a cyanide bath for seconds and given a clear protective lacquer coating. The resulting lacquered copper plated surface had a pleasing uniform small grained pattern.

Example 9 A buied panel-.of 30% zinc and 70% copper was cleaned as in Example 1 and then transferred to an aqueous anodizing bath containing 45 g./l. of a mixture of 60% sodiumsilicate G and 40% of anhydrous sodium carbonate. The panel was anodized therein for 15 seconds at 180 F. at a voltage of 3 volts without agitation. The anodized panel was then rinsed, acid dipped and rinsed again and transferred to a nickel plating bath of the same composition as in Example 3 wherein it was given a nickel plate 0.2 mil thick. A flash of chromium was plated over the nickel. The finished surface had a very uniform pleasing pattern.

Example 10 A 30:70 brass panel was cleaned and copper plated in a. high speed copper cyanide bath and then buffed and cleaned as in Example 1. The cleaned panel was transferred to an aqueous anodizing bath of the same composition yas in Example 7 and anodized therein for 15 seconds at 180 E. at 3 volts and a current density of 4-6 a. s. f. The anodized panel was then immediately rinsed, acid dipped, and rinsed again and transferred to a nickel plating bath of the same composition as in Example l wherein it was given a nickel plate 0.2 mil thick at E. and a current density of 30 a. s. f. A subsequent plate of. chromium was electrodeposited over the nickel plate. The resulting composite coating had a semi-bright luster revealing decorative patterns.

Example 11 A low carbon steel panel (rolled from wire stock) was buifed on one side to provide a high luster and was then cleaned as in Example 1 to provide a sound clean surface. The cleaned panel was transferred to an laqueous anodizing bath containing 45 g./l. of a mixture of 80% sodium silicate G and 20% sodium carbonate. The panel was :anodized therein for 15 seconds at 180 F. at 1 volt (0.1-0.6 a. s. f.). The resulting Lanodized panel was then immediately rinsed, acid dipped and rinsed again and given a nickel plate 0.2 mil thick from a nickel plating bath of the same composition as in Example 1. The nickel plated panel was then given a flash of chromium. The surface of the finished panel had a pleasing uniform pattern of somewhat larger grain size than that of the panels produced in the preceding examples.

Example 12 A 30:70 brass panel was buffed and cleaned as in Ex ample l. The cleaned panel was then immersed in an anodizing solution of the same composition as in Example 11 contained in a steel tank. The panel was attached to the tank by a conductor and permitted to soak without agitation in such solution for 1 minute while being sub- 7 jected to the galvanic action of steel-brass couple. no outside current being supplied. The resulting anodized panel Was rinsed, acid dipped and rinsed again and given a nickel plate 0.2 mil thick in a plating bath of the same composition as in Example 3. The nickel plated panel was then chromium plated for a few minutes. The resulting chromium surface had a pleasing uniformly grained pattern.

Example 13 A 30:70 buffed brass panel was cleaned as in Example 1 and transferred to an aqueous anodizing bath containing 50 g./l. of a mixture containing 71.6% sodium silicate G, 14.2% of anhydrous sodium carbonate and the remainder hydrated sodium tetraborate. The panel was anodized therein at F. for 60 seconds at a current density ranging from 0.6 to 1.2 a. s. f. The resulting anodized panel was then given a nickel plate 0.2 mil thick from a bath of the same composition as Example 1. The nickel plated panel was then given a flash of chromium. A decorative pattern appeared through the chromium plate.

I claim:

l. A method of producing a decorative finish upon a metal object selected from the group consistingof copper, brass, and steel objects which comprises anodizing such metal object in an alkaline aqueous silicaceous solution having a pH of between 10.25 and 12.2 to produce an invisible -anodic film thereon and thereafter electroplating such anodized object still carrying such anodic lilm in a bright nickel plating bath until a patterned nickel plate is produced.

2. The method of claim l, in which said silicaceous solution has a pH of 10.75 to 12.0.

3. The method of claim 1, in which said alkaline aqueous silicaceous solution is an aqueous solution of an alkali metal silicate having 'a pH between 10.25 and 12.2.

4. VThe method of claim l, in which said alkaline aqueous silicaceous solution is an aqueous solution of a colloidal hydrated silica having a pH between 10.25 and 12.2.

5. The method of claim 1, in which said alkaline silicaceous solution contains 2 to 20 grams of SiOz per liter.

6. The method of claim 1, comprising in addition electroplating such patterned nickel plated object with another metal from a bright plating bath.

7. A method of producing Ia decorative huish upon a metal object selected from the group consisting of copper, brass, and. steel objects which comprises anodizing such metal object in an alkaline aqueous silicaceous solution having a pH of between 10.25 and 12.2 to produce an invisible anodie Film thereon, stamping a portion of the surface bearing the invisible anodic film with a stamp of resilient rnbbery material and thereafter electroplating such anodized object still carrying such anodic film in a right nickel plating bath until a patterned nickel plate is produced.

8. A method of producing a decorative finish upon a metal object selected from the group consisting of copper, brass, and steel objects which comprises polishing and cleaning the surface of such objects to provide a lustrous sound surface, anodizing such metal object in an alkaline aqueous silicaceous solution having a pH between 10.25 and 12.2 at a temperature between 160 and 180 F. to produce an invisible anodic lm thereon, rinsing the anodized object before the silicaceous solution has an opportunity to dry and thereafter electroplating such rinsed anodized obj'ect still carrying the anodized lm in a bright nickel plating bath until a patterned nickel plate is produced.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Principles or Eleetroplating and Electro Forming, Blum and Hoganboom, pages 21l-219, McGraw-Hill Book 0 Co. Inc., New York (1949), 3rd edition. 

1. A METHOD OF PRODUCING A DECORATIVE FINISH UPON A METAL OBJECT SELECTED FROM THE GROUP CONSISTING OF COPPER, BRASS, AND STEEL OBJECTS WHICH COMPRISES ANODIZING SUCH METAL OBJECT IN AN ALKALINE AQUEOUD SILICACEOUS SOLUTION HAVING A PH OF BETWEEN 10.25 AND 12.2 TO PRODUCE AN INVISIBLE ANODIC FILM THEREON AND THEREAFTER ELECTROPLATING SUCH ANODIZED OBJECT STILL CARRYING SUCH ANODIC FILM IN A BRIGHT NICKEL PLATING BATH UNTIL A PATTERNED NICKEL PLATE IS PRODUCED. 